It is normally
superior to prayer on the ground itself, especially if it is clean.

It is permitted
to pray on a carpet, prayer mat, and the like, without it being disliked,
as the fuqaha have mentioned. [Ibn Qudama, al-Mughni, 1.408; al-Fatawa
al-Hindiyya, 1.63; and other works.]

This is based
on many hadiths that indicate that the Prophet (Allah bless him & give
him peace) prayed on a carpet. [Bukhari, Muslim, Ahmad, Tirmidhi, Ibn Maja,
and others.]

Imam Tirmidhi,
the great hadith expert, reported that this was the position of most of
the people of knowledge from the Companions and those after them, and the
position of the overwhelming majority of the fuqaha.